Oil-in-water type emulsion comprising vegetable sterols

ABSTRACT

The purpose of the present invention is to provide oil in water type emulsion supplemented with phytosterol, and having an excellent emulsion stability during storage. The present invention relates to oil in water type emulsion comprising ester-type phytosterol of 1.5˜50%, and free-type phytosterol of 0.01˜1.0% of oil phase of the emulsion.

TECHNICAL FIELD

The present invention relates to an oil-in-water (O/W) type emulsionsupplemented with phytosterol. The “pytosterol” in this specificationrefer to a general concept that comprises both free- andester-components of the phytosterol. The free component of thepytosterol will be referred to hereinafter as a “free-type phytosterol”,and its ester component as an “ester-type phytosterol.”

BACKGROUND ART

Vegetable oil widely contains a slight amount of phytosterol such asβ-sitosterol, stigmasterol and campesterol in the form of the free-typephytosterol and the ester-type phytosterol.

For example, rape oil contains 0.3˜0.7% of the ester-type phytosteroland 0.2˜0.4% of the free-type phytosterol; corn oil contains 0.3˜0.8% ofthe ester-type phytosterol and 0.1˜0.4% of the free-type phytosterol;and soybean oil contains 0.1˜0.5% of the ester-type phytosterol and0.1˜0.4% of the free-type phytosterol.

Recently, a cholesterol-lowering effect due to the phytosterol has beennoticed, and water-in-oil (WIO) type emulsion such as fat spread is nowcommercially available.

However, among phytosterol produced as edibles, the free-typephytosterol is hardly soluble both in water and oil, and the ester-typephytosterol is hardly soluble in water. Some adjustment will be neededin the formulation of foods comprising them.

When compared with the W/O type emulsion such as fat spread, the O/Wtype emulsion has more problems that a drastic increase in particle sizedue to aggregation of oil drops and the phase-transition of emulsionwill cause reduction in emulsion stability, making it liable to inducethe destruction of emulsion during storage, especially under loads suchas shaking during distribution or transportation.

Techniques such as those to reduce a ratio of oil phase or to add anemulsifier were tried in order to overcome the above destruction of theemulsion. However, the reduction of the ratio of oil phase wouldeliminate body taste, and an excess amount of the added emulsifier woulddeteriorate its taste.

The representative related techniques in the art will be listed asfollows.

First, the Japanese Patent Application Publication Hei 11(1999)-506324(the applicant: Unilever N.V.) discloses an invention relating tofat-based foods defined by their components and contents for the purposeof lowering cholesterol in serum. However, although it disclosesbutter-like spread, dressing, coffee creamer, and shortening as theexamples of the fat-based foods, it does not refer to O/W emulsion thathas a stability-related problem It describes that esterification wouldrather be a non-preferable embodiment (page 14, second paragraphs beforeExample 1).

Second, the Japanese Patent Application Publication Hei 11 (1999)-146757(the applicant: Unilever N.V.) discloses an invention relating to astable aqueous dispersion or suspension and its use for foods, enablingthe use of fat/oil having a high melting point such as phytosterol. Italso describes that the diameter of the particles of said fat/oil andthe amount of an emulsifier should be limited in order to use saidfat/oil, and that non-esterified sterol would be most advantageouslyapplied (the paragraph 45).

Third, the Japanese Patent Application Publication Hei 11(1999)-127779(the applicant: Unilever N.V.) discloses an invention relating to foodscontaining sterol-containing fat and having a cholesterol-loweringeffect. The invention aims at resolving the problems involved in theesterification of the phytosterol that it will reduce thecholesterol-lowering effect in serum, and that it will also need a longtime and a high cost for its processes.

Forth, the Japanese Patent Application Publication 2000-102361 (theapplicant: McNeil PPC., Inc.) discloses an invention relating to amethod for the production of salad dressing containing sterol ester,which is stable even under refrigeration (the paragraph 0001). Theinvention is characterized by comprising an emulsifier or hydro-colloid,and an inhibitor against crystallization of fat. With respect to thesterol ester, it does not describe or suggest a degree ofesterification, but just discloses a supplying amount of P-sitosterolfor the purpose of decreasing the amount of cholesterol.

The purpose of the present invention is to provide an O/W type emulsionsupplemented with phytosterol, which has a high emulsion stability.

DISCLOSURE OF THE INVENTION

The present invention is related to an O/W type emulsion comprisingester-type phytosterol of 1.5˜50%, and free-type phytosterol of0.01˜1.0% of oil phase in the emulsion.

Although a part of the phytosterol is removed in a deodorizing step andthe like during purification processes of oil, general kinds of ediblevegetable oil contain a slight amount of both the ester-type phytosteroland the free-type phytosterol. For example, as already mentioned above,rape oil contains 0.3˜0.7% of the ester-type phytosterol and 0.2˜0.4% ofthe free-type phytosterol; corn oil contains 0.3˜0.8% of the ester-typephytosterol and 0.1˜0.4% of the free-type phytosterol; and soybean oilcontains 0.1˜0.5% of the ester-type phytosterol and 0.1˜0.4% of thefree-type phytosterol. When the O/W type emulsion is prepared using suchkinds of oil, the emulsion stability will be kept during storageincluding distribution or transportation.

However, at least a certain amount of the phytosterol has to in order toshow the lowering effect of cholesterol in serum. The same effect isattributed to inhibition of cholesterol absorption by the free-typephytosterol. The ester-type phytosterol will show the same effect afterbeing decomposed into its free component. However, when the ester-typephytosterol is purified from oil/fat in the prior arts, the amount ofthe free-type phytosterol will be simultaneously increased. It has beentherefore difficult to prepare a stable O/W emulsion taking theproperties of both the ester-type phytosterol and the free-typephytosterol into consideration.

The ester-type phytosterol may be generated by esterification orester-exchange reaction of the free-type phytosterol with fattyacid-containing substances such as triglycerides, fatty acids and methylester of fatty acids. However, unreacted free-type phytosterol willstill remain in such reaction. Accordingly, it is difficult to preparethe stable O/W emulsion taking the properties of both the ester-typephytosterol and the free-type phytosterol into consideration.

“%” means “% by weight” in the present specification unless otherwisespecifically defined. Similarly, the numbers in the Examples of thepresent specification should be understood as expressed in units of % byweight as well.

There is no limitation with respect to the kinds of phytosterol,including any one known to those skilled in the art such asβ-sitosterol, stigmasterol and campesterol. There is no limitation withrespect to oil/fat to be mixed with the phytosterol as long as it isedible, being preferably rape oil, corn oil and soybean oil in respectof costs, taste and versatility.

The present O/W type emulsion comprises the ester-type phytosterol of1.5˜50%, preferably of 5˜35% of the oil phase in the emulsion. A moreamount of the ester-type phytosterol would not be preferable in view ofcosts and stability, and a less mount of the ester-type phytosterolcould not show a sufficient cholesterol-lowering effect.

The present O/W type emulsion comprises the free-type phytosterol of0.01˜1.0%, preferably of 0.3˜0.6% of the oil phase in the emulsion. Amore amount of the free-type phytosterol would deteriorate the emulsionstability, and a less mount of the free-type phytosterol would not bepreferable in view of production costs.

A ratio of the oil phase in the present O/W, type emulsion rangespreferably between 50 and 90%, more preferably between 60 and 80%. Ahigher ratio would be liable to cause phase transition. As a lower ratiowould have tendency of improving the emulsion stability, the specificadvantages of the present invention will be especially recognized whenthe ratio of the oil phase is 50% or more.

Furthermore, it is desired for the present invention to effect itsadvantages that esterification degree of the phytosterol in the oilphase of the present invention is preferably higher than 90, morepreferably higher than 95. The esterification degree is a value that isobtained by the following equation:

Esterification Degree:(Content of the ester-type phytosterol in the oil phase (mol))/(Totalcontent of the ester-type phytosterol and the free-type phytosterol inthe oil phase (mol))×100

Other emulsifiers than egg material, which contribute to the emulsionstability, may be used in the present invention in order to improve it.However, since the emulsion of the present invention is stable evenwithout using any emulsifier, the advantages of the present inventionwill be more significantly observed in the O/W type emulsion withoutcomprising any emulsifier in view of taste and costs. The emulsifier inthe present invention includes xanthan gum, low cast bean gum, carrageenand a thickening gent such as agar, in addition to emulsifiers such assucrose ester, fatty acid ester of polyglycerine and enzyme-treated egg.

The O/W type emulsion of the present invention may be prepared by anygeneral method known in the art. It may be prepared, for example, bypre-mixing water phase and oil phase and emulsifying the mixture to astate having given properties by means of colloid mill, by reference to,for example, Chuhei IMAI, “Knowledge about Mayonnaise & Dressing”,published by Saiwai Publishing Company, 1993, p. 107-134.

Phytosterol with a decreased ratio of its free-type in the O/W typeemulsion of the present invention may be prepared by any general methodknown in the art. For example, the ratio of the free-type phytosterolmay be optionally decreased by esterifying the free-type phytosterol bymeans of sodium methylate and the like, and controlling the conditionsof a steam distillation to a strong level

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be explained in more detail with reference tothe following examples, which should not be construed as limiting atechnical scope of the present invention.

In the following examples, the ratio of the free-type phytosterol wasoptionally decreased. Thus, the content of the free-type phytosterol inthe phytosterol was adjusted to a determined value by esterifying thefree-type phytosterol with fatty acids by means of sodium methylate andcontrolling the conditions of a steam distillation to a strong level.

The following examples were carried out with reference to Chuhei IMAI,“Knowledge about Mayonnaise & Dressing”, published by Saiwai PublishingCompany, 1993, p. 107-134.

The contents of total sterol, the ester-type phytosterol and thefree-type phytosterol were determined as follows.

Determination Method of a Total Amount of Sterol in the O/W TypeEmulsion

[Saponification]

O/W type emulsion (0.5 g) is weighed in an Erlenmeyer flask with frost(with a glass stopper), followed by the addition of ethanol solution (25ml) of 2 mol/l of potassium hydroxide and pyrogallol (25 ml). A refluxcondenser is attached to the flask, which is then heated on a water bathat 90° C. or more for one hour for saponification. The saponificatedproduct is transferred into a separating funnel, mixed with water (150ml) and ethyl ether (diethyl ether) (50 ml), stirred, and kept standingstill to be separated into two phases. The lower phase is then taken,washed with water, and dried by means of an evaporator. The extract isdissolved in ethyl ether (3 ml), a part of which (1 ml) is reacted withTMSI-H (5 ml), and mixed with acetone (1 ml). The upper phase issubjected to GC analysis.

[GC Analysis Conditions]

-   Column: CP-Sil8CB (0.25 mm×30 m);-   Injector Temp.: 280° C.;-   Detector Temp.: FID 290° C.;-   Oven program: 260° C. (50 min.), 10° C./min, 300° C. (5 min.);-   Split ratio: 50:1;-   Column Flowing rate: 1.4 ml/min.    Determination of the Free-type and Ester Type Phytosterol    [TLC Fractionation and GC Analysis]

O/W type emulsion (5 g) is weighed in a n Erlenmeyer flask, kept forseparation, mixed with methanol (50 ml) and chloroform (100 ml), andthen transferred into a separating funnel. After the solution issufficiently stirred, it is mixed with 0.9% sodium chloride solution,stirred and allowed to stand still. Chloroform phase is then taken,filtered and dried to solid. An appropriate amount of a solution of theresulting solid in ethyl ether is applied on a HPTLC plate, developedwith a solution of hexane 70%/ethyl ether 30%, dried and reacted withiodine to develop color. The spots of the free-type phytosterol and theester-type phytosterol are picked up by scratching, respectively,extracted with a solution of chloroform 50%/methanol 50%, and dried tosolid. The resulting solid is saponificated and subjected to GC analysisin the same manner as in the above “Determination Method of a TotalAmount of Sterol in the O/W type emulsion.” An amount of each type ofthe phytosterol is obtained by multiplying the total amount of sterol byeach ratio.

[HPTLC Conditions]

-   HPTLC plate: 25HPTLC plate Silicage1160 (Merk Co.);-   Developing agent: hexane 70%/ethyl ether 30%

EXAMPLE 1

Egg (8%), starch syrup (4%) and others (8.5%) including salt, seasoning,lemon juice, spice and water were manually stirred and mixed. Afterfurther being mixed with vinegar (7.5%), rape oil (57%) and phytosterol(15%) having three different ratios of the ester type and the free-typephytosterol, the resulting mixture was put into a hobart mixer, mixed tobe emulsified in a homo genized state. It was further emulsified bymeans of a colloid mill emulsifier to give O/W type emulsion of thepresent invention 1, the present invention 2 and comparative example 1,respectively.

A polyethylene bag (inner size: 7×12 cm) was filled with each resultingO/W type emulsion (50 g) and subjected to a shaking test under theconditions of shaking width: 2 cm, shaking rate: 250 times/min, and testtime: 30 min so as to observe occurrence of the separation of oil.

The composition of the O/W type emulsion and test results are shown inTable 1.

The figures in the columns of “Free-type phytosterol (in oil phase)” and“Ester-type phytosterol (in oil phase)” mean the content of eachphytosterol contained in the oil phase such as edible vegetable oil orphytosterol. The symbols of “x”, “◯”, and “⊚” in the column “Storagestability” mean “occurrence of the separation of oil”, “occurrence of aslight separation of oil, which will not deteriorate the quality ofproducts under usual storage conditions”, and “no occurrence of theseparation of oil” after the shaking test, respectively.

TABLE 1 Comparative Present Present example 1 invention 1 invention 2Rape oil 57 57 57 Phytosterol 15 15 15 Egg 8 8 8 Vinegar 7.5 7.5 7.5Starch syrup 4 4 4 Salt, Seasoning, Lemon 8.5 8.5 8.5 Juice, Spice andWater Total 100 100 100 Ester-type phytosterol (in oil 19.65 20.28 20.69phase) Free-type phytosterol (in oil 1.46 0.83 0.42 phase)Esterification degree 89.2 93.7 96.8 Storage stability X ◯ ⊚

EXAMPLE 2

The O/W type emulsion was prepared by using the same apparatuses as inExample 1. Thus, Egg (9%), and others (10%) including starch syrup,salt, seasoning, lemon juice, spice and water were manually stirred andmixed.

After further being mixed with vinegar (7.5%), blended oil (63%)(rapeoil: corn oil=70:30) and phytosterol (10%) having three different ratiosof the ester type and the free-type phytosterol, the resulting mixturewas put into a hobart mixer, mixed to be emulsified to a homogenizedstate. It was further emulsified by means of the colloid mill emulsifierto prepare O/W type emulsion of the present invention 3, the presentinvention 4 and comparative example 2, respectively.

The above composition were subjected to the same shaking test as inExample 1 and observed the occurrence of the separation of oil. Themeaning of the symbols and figures in the columns of “Free-typephytosterol (in oil phase)” and “Ester-type phytosterol (in oil phase)”,and “Storage stability” are the same as in Example 1.

TABLE 2 Comparative Present Present example 2 invention 3 invention 4Rape oil 44 44 44 Corn oil 19 19 19 Phytosterol 10 10 10 Egg 9 9 9Vinegar 8 8 8 Starch syrup, Salt, 10 10 10 Seasoning, Lemon juice, Spiceand Water Total 100 100 100 Ester-type phytosterol (in oil 13.16 13.5513.85 phase) Free-type phytosterol (in oil 1.03 0.64 0.34 phase)Esterification degree 88.7 92.8 96.1 Storage stability X ◯ ⊚

EXAMPLE 3

The O/W type emulsion was prepared by using the same apparatuses as inExample 1. Thus, Egg (10%), and others (7%) including sugar, salt,seasoning, lemon juice, spice and water were manually stirred and mixed.After further being mixed with vinegar (3%), soybean oil (52%) andphytosterol (28%) having three different ratios of the ester type andthe free-type phytosterol, the resulting mixture was put into a hobartmixer, mixed to be emulsified to a homogenized state. It was furtheremulsified by means of the colloid mill emulsifier to prepare O/W typeemulsion of the present invention 5, the present invention 6 andcomparative example 3, respectively.

The above composition were subjected to the same shaking test as inExample 1 and observed the occurrence of the separation of oil. Themeaning of the symbols and figures in the columns of “Free-typephytosterol (in oil phase)” and “Ester-type phytosterol (in oil phase)”,and “Storage stability” are the same as in Example 1.

TABLE 3 Comparative Present Present example 3 invention 5 invention 6Soybean oil 52 52 52 Phytosterol 28 28 28 Egg 10 10 10 Vinegar 3 3 3Sugar, Salt, Lemon juice, 7 7 7 Spice and Water Total 100 100 100Ester-type phytosterol (in oil 32.52 33.61 34.38 phase) Free-typephytosterol (in oil 2.31 0.98 0.45 phase) Esterification degree 89.694.4 97.9 Storage stability X ◯ ⊚

INDUSTRIAL APPLICABILITY

The present O/W type emulsion, which is characterized by having oilphase containing a low content of the free-type phytosterol, hasexcellent storage stability without causing a partial separation of oilduring not only use but also distribution.

1. An oil in water emulsion, comprising: 52-63% of at least one oilselected from the group consisting of rape oil, corn oil and soybeanoil, 10-28% of phytosterol, 8-10% of egg, 3-8% of vinegar, 7-12.5%, intotal, of additional ingredients, wherein the additional ingredientscomprise water, wherein the oil phase of the emulsion contains13.55-34.38% of phytosterol ester, the oil phase of the emulsioncontains 0.34-0.98% of free phytosterol, and wherein the esterificationdegree of the phytosterol is higher than
 90. 2. The oil in wateremulsion of claim 1, wherein the oil is rape oil.
 3. The oil in wateremulsion of claim 1, wherein the oil is corn oil.
 4. The oil in wateremulsion of claim 1, wherein the oil is soybean oil.
 5. The oil in wateremulsion of claim 1, wherein the oil is rape oil and corn oil.
 6. Theoil in water emulsion of claim 1, comprising 52-57% of the oil.
 7. Theoil in water emulsion of claim 1, comprising 57-63% of the oil.
 8. Theoil in water emulsion of claim 1, comprising 10-15% of the phytosterol.9. The oil in water emulsion of claim 1, comprising 15-28% of thephytosterol.
 10. The oil in water emulsion of claim 1, comprising 8-9%of the egg.
 11. The oil in water emulsion of claim 1, comprising 9-10%of the egg.
 12. The oil in water emulsion of claim 1, comprising 3-7.5%of the vinegar.
 13. The oil in water emulsion of claim 1, comprising7.5-8% of the vinegar.
 14. The oil in water emulsion of claim 1,comprising 13.55-20.28% of the phytosterol ester in oil phase.
 15. Theoil in water emulsion of claim 1, comprising 20.28-34.38% of thephytosterol ester in the oil phase.
 16. The oil in water emulsion ofclaim 1, comprising 0.34-0.45% of the free phytosterol in the oil phase.17. The oil in water emulsion of claim 1, comprising 0.45-0.64% of thefree phytosterol in the oil phase.
 18. The oil in water emulsion ofclaim 1, comprising 0.64-0.98% of the free phytosterol in the oil phase.19. The oil in water emulsion of claim 1, wherein the esterificationdegree of the phytosterol is higher than
 95. 20. The oil in wateremulsion of claim 1, wherein the esterification degree of thephytosterol is 92.8-97.9.
 21. The oil in water emulsion of claim 1,wherein the additional ingredients further comprise starch syrup, salt,spice and lemon juice.